(1) Field
The disclosed methods and systems relate generally to semiconductor processing, and more particularly to wafer handling methods and systems.
(2) Description of Relevant Art
Some challenges of semiconductor manufacturing include providing a manufacturing process that produces reduced process defects with increased process throughput. These manufacturing concerns can also be balanced with other requirements that include a need for reduced contamination.
FIG. 18 provides one semiconductor wafer processing system 10 where, for example, a cassette of semiconductor wafers (“wafers”) can be presented to left and right load locks 12, 14 to allow wafer transfers to a processing chamber 16 such as, for example, an ion implantation chamber. The load locks 12, 14 can be understood to be an interface between a loading station and the processing chamber 16. Because the wafers can be loaded from a loading station that may often be at atmospheric pressure, once the wafers are presented to the load locks 12, 14, the lock loads 12, 14 can be isolated from the loading station and the processing chamber 16. A load lock vacuum pump, for example, can thus reduce the load lock pressure, or “evacuate” a respective load lock 12, 14, in accordance with, or to be consistent with the processing chamber pressure.
Wafers from the cassettes in the left and right load locks 12, 14 can be processed in turn, alternating between left and right load locks 12, 14. Accordingly, in a system according to FIG. 18, the left and right load locks 12, 14 can be substantially simultaneously evacuated and thereafter opened or otherwise interfaced to the processing chamber 16. For exemplary purposes, a left arm 18 can retrieve a wafer from the left load lock cassette, and present the retrieved wafer to a left orienter 20 that can locate a wafer notch to align the wafer center with the orienter axis of centricity. The left arm 18 can thereafter deliver the wafer to a platen 22 in the process chamber 16, and thereafter, the left arm 18 can be displaced to allow wafer processing. Once the wafer is processed, the left arm 18 can deliver the wafer from the platen 22 to the left orienter 20 and hence to the left load lock cassette. As FIG. 18 indicates, a wafer from the right load lock cassette can be retrieved by a right robot 24 and placed on a right orienter 26 before being delivered to the platen 22 for processing. Such wafer can also be returned to the right load lock 14 after processing is complete. As provided previously herein, throughput for a system according to FIG. 18 can be improved by coordinating the alternating delivery of wafers from the left and right load lock cassettes to reduce delay between deliveries to the platen 22.
For a system according to FIG. 18, once the wafers from the left and right load lock cassettes are processed and returned to the load lock cassettes, the load locks 12, 14 can be isolated from the processing chamber 16 to allow a substantially simultaneous venting of the load locks 12, 14 and a return to a pressure according to, or otherwise consistent with the loading station pressure. The interfaces between the respective load locks 12, 14 and the loading station(s) can then be opened to allow transfer of the left and right cassettes in accordance with a processing methodology.
Batch vacuum load locks such as those according to FIG. 18 can experience poor cycle time because the larger volume of a batch load lock can present a longer evacuation time, during which wafers are being processed from neither the left nor right load locks 12, 14.